1. Field of the Invention
The invention in general relates to position indication systems, and particularly to a system for determining the position of control rods within a nuclear reactor.
2. Description of the Prior Art
Various systems exist which include members which move between set limits with a requirement for remotely sensing the position of the movable member. For example, in the field of nuclear reactors, it is necessary to raise and lower control rods within the reactor core for controlling the energy output of the nuclear reactor.
In one type of system, the control rods are relatively moved into and out of the reactive region (the nuclear core) positioned within a pressure vessel, with the control rods being connected to respective drive rods. These drive rods are movable within respective sealed pressurized rod travel housings and longitudinal movement is imparted by means of a drive mechanism.
Inasmuch as the control rod is connected to the drive rod, an indication of control rod position may be obtained by detecting the position of the drive rod as it moves within its housing. The position of the drive rod within its housing is obtained without any penetration of the housing by means of a detector assembly having a plurality of coils disposed around the housing and along the path of movement of the drive rod. The materials are such that as a rod is moved through the center of a coil, the impedance of the coil will noticeably change. The coils are connected to signal processing apparatus for detecting this change to thereby provide an indication of drive rod, and therefore control rod position.
The signal processing apparatus is located in the same containment structure that includes the nuclear reactor and along with other signal processing circuitry, interacts with a remote central control station. A typical installation may have between 30 and 70 drive rods and associated detectors such that a relatively large number of signal processing circuits are required in the containment environment.
In many instances, it would be desirable to minimize the signal processing equipment required within the containment structure and even to remove it therefrom entirely. The present invention accomplishes such objective.